This application relates to an electrical machine that may be a starter/generator, or may be a motor drive, and wherein power switches are integrated with motor coils, with a current source inverter positioned between a power source and a machine. The application also relates to unique power supply architecture for use on a vehicle such as an aircraft.
Electrical machines are known, and will include a plurality of coils. The electrical machine can operate as a motor or as a generator. A switching network including a plurality of transistors and diodes is positioned to be in series with the coils. It is known to integrate the switching network and the coils within a single housing that offers benefits discussed above.
In the past, such machines have been provided with a voltage source inverter. A voltage source inverter typically includes a DC link capacitor, as an energy storage device. When such a capacitor is incorporated within the housing packaging problems arise due to large size and sensitivity to temperature and current ripple on a DC bus.
Integration of an electrical machine and a motor drive into a single housing eliminates long cables between a motor and motor drive, eliminates standing voltage waves between the motor and motor drive, and reduces or eliminates a filter at the motor drive output.
Progress is made by integrating an electrical machine and a voltage source inverter (VSI). However, a VSI has undesirable characteristics including a need for a large size DC link capacitor, as an energy storage device, and shoot-through concerns. Integration of a VSI with the motor housing can be significantly improved by utilizing silicon carbide (SiC) power semiconductors such as SiC MOSFETs, SiC JFETs, SiC BJTs and SiC Schottky diodes. High temperature SiC devices can simplify cooling arrangements.
However, the use of a DC link capacitor in a VSI creates packaging challenges due to its large size, and sensitivity to operating temperature and current ripple on DC bus. Film capacitor ripple current rapidly decreases with temperature. Other drawbacks of a VSI are associated with the pulse-width modulated voltage waveforms resulting in high electromagnetic interference (EMI) noise, bearing-leakage currents, and high stress on motor insulation.
Current source inverters are known, and rely upon a DC link inductor as an energy storage device. However, such current source inverters have not been incorporated into a housing with a switching network and motor drive coils as mentioned above.